Method of driving electric centrifugal machines



5. 0. MACKINTOSH, METHOD OF DRWING ELECTRIC CENTRIFUGAL MACHINES.

APPLICATION HLED NOV- 1], 19KB.

Patented June 1,1929.

INVENTOR En rwmza 21 By MflCKI/V ros H J I ATTORNEYS UNITED STATESPATENT OFFICE,

EDWARD I). MACKIIN'TOSH, OF BROOKLYN, NEW YORK, ASSIGNOR TO S. S.HEPWORTH COMPANY, OF NEW YORK, N, Y., A. CORPORATION OF NEW YORK, ANDEDITH M. MAOKINTOSH, OF BROOKLYN, NEW YORK.

'umnon'or nmvnre nnnc'rnrc osn'rarruoan naonmns.

Specification of Letters Patent.

Application flied November 11, 1918. Serial No. 282,051.

To all whom it may concern: Be it known that I, EDWARD D. MA01I N 'rosH,a citizen of the United States, residing at Brookl n, iri'the county ofKings and the State of ew York, have invented an Im roved Method ofDrivin Electric Gen tri ugal Machines with echanical Unloaders.

Centrifugal machines are run at a high speed, the most popular sizemaking about 1000 revolutions per minute when drying sugar whereas themust make onlyabout 20 while being ischar ed by means of mechanicalunloaders. he problem is, to obtain these two speeds with a centrifugalmachine driven by an electric motor, especially by an induction motor.ltis entirely impracticable to get the two speeds by braking down theinduction motor from the higher speed orby giving it two windings. 5

One reason that'they can not be had braking down from the higher speedis, that the rush of current, at the lower speed,

This could be reduced by the use of a transformer, but the field wouldstill be rotating at the higher speed while the rotor would be at thelower speed. This would result in objectionable heating if, indeed, themotor would stand it at all.

As for two windings, it is practically impossible to make two sodissimilar as to give anything like two speeds so far apart as 20 and1000. v

I achieve the desired result by using a two speed motor and employingthe form of drive that connects the motor to the centrifugal machine bmeans of a centrifugal friction clutch. his well known form of drive hasblocks, restin loosely in a cup secured to the spindle o the centrifugalmachine,

that are revolved in the'cu by means of .a

driver secured to the s in lo of the motor and that are held tofrictionalcontact with" the inside of the cup by centrifugal force. Inpractice I find that it works well to run the motor at half the speed,for driving the machine against the unloader that is used while it isdoing its work. Ifalf the s eed means one quarter of the centrifugalorce' and of the resulting frictional grip of the blocks on the cup. Onequarter the torque at one half the speed results in no objectionabout1200 600 R. P. M. The iotor shaft 9 is-vertical or rush of current andthe recient, or more than sufficient, to drive the centrifugal machine aainst the 'unloader. When just snflicient, tie speed of the machine canbe he t down to the 20 revolutions or so, desired, y the braking effectof the unloader itself, the motor continuing to run at one half of itsmaximum speed while the blocks slip in the cup. When more thansufficient, the extra braking effect required, to keep the speed down,is had by means of the brake forming part of every centrifugal machine.

c In the accompanying drawing a centrifugal machine is shown partiallyin vertical section, in which my invention is embodied in one form.

As here illustrated, the electric motor, enerally indicated 'by'thereference a, has

its winding 6 (for either direct or alternat-.

ing current) of such nature as'to afford a multlple spaced drive,preferably one at P. M., and the second at about and runs in upper andlower ball bearings c and allocated in oil chambers e and frespectively.

At the lower end of the motor shaft and below the bearing (i is securedone element viz., the spider h, of a centrifugal clutc The s idercarries a roup of swinging or sliding blocks 11 whlch, when the motor isrotated, are thrown outward into engagement with the clutch ring j. Thelatter is bolted to the clutch plate 0, which in turn is clamped rigidlyto the head of the shaft m of the centrifugal basket t.

The relation of the clutch blocks a to the ringjis such that they do notengage the latter until the motor is well under i? and even at the lowerspeed (600 R. P.

of the motor the torque exerted by the clutch is only about one fourththat exerted when the motor is' at high working speed. The slip of theblocks on the ring at low speed of the motor is therefore a matter of nogreat moment from the standpoint of wear or overheating of these parts.

The support for the shaft m of the centrifugal basket may be of anysuitable construction, but is here shown as of the t pe disclosed in mycopending application en Patented June 1, 1920.

No. 296,908 filed May 13, 1919. It comprises a ball bearin Z mounted ina cup 8 which is supported in the frame of the centrifugal through theball and socket joint r,so as to permit'the basket t to swing slightly.

Theunloader plow 'w is carried by racket o'mounte'd on the centrifugalbasket 'cas ing a, and is lowered and lifted 'by means of its rack bar yengaged by a pinion on the shaft of the crank' handle an. The usualbrake drum p is fast on the upper portion of the shaft m and is enga edy the brake band 9 in well understoo manner to halt the basket whendesirable.

The installation 0 crates vas above set forth. During the dryi operationthe motor is run at high spee 1200 R. P. M.). When the material is driedand the valve in the bottom of the basket has been opened to permit itsdischai' ge the motor is run at low speed (600 R. M -When the dischargerplow w is swung by the operator into engagement with the material liningthe interior of the basket, it exerts a drag upon the latter whichcauses the friction clutch to slip, and thus dropsthe s eed. of

revolution to that convenient for un oading- (about 20 R. P. M.). Theextent of the drag thus exerted by the plow is wholly under the controlof the o erator, since the more rapidly the plow is owered the greaterthedrag, and vice verse. By a proper mam ulation of. the plow thenecessary regula on V of the drag is attained to secure the properdischarge s eed of revolution of the basket.

Of course t e o eratormay at an time is sort to the ad itional control aorded by the brake, but this is-not ordinarily rescope of the latterbeing in no way limited thereby.

I claim 1. A centrifugal machine com risin a multispeed electric motor,a centri ugal asket or the like, a friction clutch drive connectionbetween the motor and the basket, thelow speed drive of the motorexceeding av p'ropeiE unloading speed, in combination with an nloaderserving by its drag on the material n the basket to cause the frictionclutch to slip and thus to reduce the s eed of the basket to onesuitable for unloa ing, substantially as described.

2. In a centrifugal machine of the ty e specified inclaim 1, a frictionclutch of t e centrifugal type.

3. In a centrifugal machine of the ty e specified in claim 1 a two-speedmotor, the lower speed bein about half the high speed, and a centrifugefriction clutch exerting at low speed only about a quarter of the toru'e exerted athigh speed, substantially as described.

. EDWARD 1D. MAoKrn'rosH.

